@fiedler, not sure how you can defend the position that the US wasn't defeat in Vietnam. Withdrew troops, lost many, lost the South Vietnam government/all they were sent to prop up.
It is pretty clear. In another sense, the peace movement which spring up in opposiion to Vietnam was eventually successful, though they are never credited with a victory. They opposed the draft, and much less was said about the war before the draft was brought in, it became politically difficult at home to continue the war, so the powers that be gave up -never admitting defeat.
What is also not stated, at least publically, is the fact that later invasion have faced the same opposition at home. Even from the begining of the Iraq war, the peace movement was organised and popular. Ehat influence they have on pilicy is debatable...
What is also obvious is that the defenders of US policy will not admit there was any wrong doing - they will say Vietnam was badly prosecuted, that the war casualties made it unpopular, and that it was a good ifea badly executed. But never that the war was a bad immoral thing to do.
And yet the peace movement have said just that from the very begining. They don't oppose war because of casualties; they oppose it on moral grounds, and always have.
This is a far more nuanced and interesting conversation than the strategic level stuff (where the US clearly lost ground in Vietnam).